1. Field of the Invention
Exemplary embodiments of the present invention relate to a packet transmission/reception method and apparatus in a wireless communication system.
2. Description of Related Art
While a variety of high-capacity multimedia services have been vitalized, the performance of a wireless communication system is not high. Since multiple users share a wireless resource, the transmission speed of the wireless service, which is felt by the users, becomes significantly low. Accordingly, a variety of techniques have been researched to increase the performance of the wireless communication system for multiple users. For example, the bandwidth may be increased to expand the wireless resource shared by multiple users, or a specific beam may be implemented for communication with each user while a wireless resource having the same bandwidth is used.
A medium access control (MAC) protocol of the wireless communication system is operated on the basis of CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance). Therefore, the MAC protocol contains a problem of resource waste which occurs during a channel contention process. In order to solve such a problem, an enhanced MAC protocol defined by the IEEE 802.11 working group ‘e’ has proposed burst transmission in which multiple MAC protocol data units (MPDU) are transmitted at a short inter-frame space (SIFS) during a transmission opportunity (TXOP) time, when a transmission opportunity for a wireless resource is acquired, and a block ACK frame for the multiple MPDUs is received. Furthermore, the IEEE 802.11 working group ‘n’ has defined an aggregated MAC service data unit (MSDU) (hereinafter, referred to as A-MSDU) and an aggregated MPDU (A-MPDU). In this case, MSDUs and MPDUs may be respectively aggregated without an IFS, and then transmitted through one contention process for a wireless resource.
According to the development trend of the above-described wireless communication system, the IEEE 802.11 working group ‘ac’ has defined that the maximum performance of 1 Gbps should be supported at and a MAC service access point (SAP) of an access point (AP) in a wireless communication system including one AP and two stations (STA), and the maximum performance of 500 Mbps is required at a MAC SAP of an STA for a point-to-point environment, in order to implement a high-speed wireless communication system. Furthermore, as the requirements of the high-performance wireless communication system, each AP and STA needs to support compatibility with the existing wireless communication system (IEEE 802.11a/n system).
In the wireless communication system, a transmitter (AP or STA) acquires a wireless channel, and then transmits data having a byte-unit length and information required for transmitting the data together. A structure including the data and the information required for transmitting the data may be referred to as a packet. At this time, the information required for transmitting the data is defined as a promised value in a structure named ‘header’.
FIG. 1 shows the structure of a packet defined in the IEEE 802.11a. Data having a constant byte-unit length and a variety of fields are configured together and then transmitted to a receiver, and the receiver receives the data by using information acquired from the respective fields. The variety of fields include short and long training fields 11 and 12, a signal field 13, a service field 14, and tail & pad fields 16, which contain information required by a physical layer (PHY). At this time, the data included in a data field 15 as well as the service field 14 and the tail & pad fields 16 has a variable length within the maximum range.
FIG. 2 shows the structure of a packet having a mixed format, which may be received by both of the IEEE 802.11a system and the IEEE 802.11n system. Referring to FIG. 2, as the packet having a mixed format includes legacy fields 21 such as a legacy-short training field (L-STF), a legacy-long training field (L-LTF), and a legacy-signal field (L-SIG), the IEEE 802.11a system may acquire information required for receiving data. Furthermore, the packet includes fields 23 for the IEEE 802.11n system from an HT-SIG field such that the IEEE 802.11n system may acquire information required for receiving data.
As the packet structures as shown in FIGS. 1 and 2 are defined in the IEEE 802.11a and 802.11n wireless communication systems, there is a demand for a packet structure which coincides with a high-performance wireless communication system capable of simultaneously transmitting different packets to multiple users, respectively. For example, the high-performance wireless communication system may include a wireless communication system based on multi-user multi-input multi-output (MU-MIMO) technology.